Measure and prepare the ingredients, making sure that everything is at room temperature
Preheat the oven to 180 deg C. Spread the almonds on a baking sheet and toast in the oven for about 8 minutes - you will be able to smell their fragrance by then.
Process 3 tbsps of the flour along with the dry blanched almonds in a food processor/ blender until ground to a fine powder.
Cream the butter and sugar till light and fluffy, in an processor or beat by hand. Fold in the lemon rind and vanilla essence.
Add the remaining flour and the ground almond flour to the butter sugar mixture and mix till the ingredients are combined into dough.
Gather the dough together, wrap in cling wrap or greaseproof paper, and refrigerate for at least an hour. You can chill the dough upto a day.
Reduce oven temperature to 325 deg F/ 170 deg C.
Line 2 baking sheets with parchment or greaseproof paper.
Mince the flaked almonds to small bits and keep aside. (skip this step if decorating with sugar)
Divide the cooled and set dough into 4 parts and work with each, as below, keeping the rest of the dough refrigerated while you work one part at a time.
Roll out each part to a thickness of about 3mm (1/8 inch) on a lightly floured surface.
Using a cookie cutter, cut out circular pieces of about 6cm each. Roll the scraps of dough flat again and cut out circular pieces, keeping the thickness uniform.
Repeat with the remaining dough until as many cookies as possible have been cut out.
Using a 2cm piping nozzle or a round cutter, cut out holes of 2cm in the middle of just half the cookie rounds so that you get an equal number of circular and ring shapes.
Arrange the circle shapes on one baking sheet and the ring shapes on another, keeping each shape about 1" apart from the next.
Whisk the white of one egg with the salt till it is frothy.
Lightly brush the Ring shapes alone, with the egg white.
Sprinkle with the minced almond flakes. (skip this step if decorating with sugar)
Place in the oven and bake for 12-15 minutes till the cookies begin to brown. Rotate the baking tray half way through.
As oven temperatures and baking times can vary, take the sheets out of the oven once you see them begin to brown.
After 5 minutes, transfer the cookies from the sheet onto a rack. if decorating with sugar, dust the sugar onto the tops (ring shapes)
Meanwhile as the cookies are cooling, add lemon juice to the jam and melt in a pan on low heat, till it comes to a simmer.
Brush the jam with a pastry brush onto the circle shapes and cover each of the circles with a ring shape so the jam comes up in the ring.
Serve immediately, or store when completely cooled, in an airtight container between layers of greaseproof sheets.